Earthshaker + Skywrath Mage

Why this works

Setting up a Mystic Flare is the core idea for this lane. Earthshaker can provide the long stun with Fissure that Skywrath Mage needs to guarantee his full damage combo with Ancient Seal. When it lands, a target usually dies. The weakness is that their synergy is very focused on this one interaction. If Fissure is on cooldown or misses, the follow-up is much less certain. Earthshaker's physical damage from Enchant Totem also gets no benefit from Skywrath's magic resistance reduction, so their damage doesn't always stack up as well as you'd think.

The game plan relies entirely on converting these setups into kills and snowballing. Together, Earthshaker and Skywrath can roam the map looking for pickoffs, creating space by forcing enemies to play defensively. But if they fail to get ahead, they have very little to fall back on. Neither hero farms especially fast, and both are vulnerable targets if caught out. An enemy team with good saves, like Glimmer Capes or Force Staffs, can often completely negate the combo, leaving both heroes out of position and with their key spells spent.